MapperConfig Names need to be unique after updating from simpleclient to metrics

[YellowFlora]

Hello,

we are currently finally updating our library away from io.prometheus:simpleclient to io.prometheus:prometheus-metrics-core.
We are using prometheus in a dropwizard library.

For this reason we configured MapperConfigs to harmonize some names.

MapperConfig mapperConfig = new MapperConfig();
mapperConfig.setMatch("org.eclipse.jetty.util.thread.*.*.jobs");
mapperConfig.setName("jetty_util_thread_jobs_count");
mapperConfig.setLabels(Map.of("type", "${0}", "pool", "${1}"));
mappers.add(mapperConfig);

Our problem now is, that our old MapperConfigs not work any longer. We always get the error, that the name needs to be unique.

org.eclipse.jetty.ee10.servlet.ServletChannel: /metrics/prometheus
! java.lang.IllegalArgumentException: jetty_util_thread_jobs_count: duplicate metric name
! at io.prometheus.metrics.model.snapshots.MetricSnapshots.<init>(MetricSnapshots.java:45)
! at io.prometheus.metrics.model.snapshots.MetricSnapshots$Builder.build(MetricSnapshots.java:99)
! at io.prometheus.metrics.instrumentation.dropwizard.DropwizardExports.collect(DropwizardExports.java:223)
! at io.prometheus.metrics.model.registry.MultiCollector.collect(MultiCollector.java:22)
! at io.prometheus.metrics.model.registry.PrometheusRegistry.scrape(PrometheusRegistry.java:85)

Changing the config to

MapperConfig mapperConfig = new MapperConfig();
mapperConfig.setMatch("org.eclipse.jetty.util.thread.*.*.jobs");
mapperConfig.setName("jetty_util_thread_${1}_jobs_count");
mapperConfig.setLabels(Map.of("type", "${0}", "pool", "${1}"));
mappers.add(mapperConfig);

would work, but we would like to avoid that we and our customers have to change all their dashboards.

Is that the desired behavior? That every name has to be unique and not the combination of name and labels?
Are there possibilities to still have the old metrics names as output, so that we don't have change the dashboards?

[zeitlinger]

This will be fixed in #696